1. Field
The following description relates to a nitride-based heterostructure field effect transistor (HFET), and more particularly, to a high efficiency nitride-based HFET capable of suppressing a leakage current of an HFET and enhancing a current density by lowering an barrier between an electrode and a semiconductor layer.
2. Description of Related Art
Recently, communications technology has developed rapidly for a high speed and high capacity signal transmission in response to global growth in information and communications technology fields. In particular, an expanding demand for a personal mobile phone, satellite communication, a military radar system, broadcast communication, a repeater for communication, and the like in wireless communication technology may lead to an increased demand for a high speed and high power electronic device to be used by an ultra high speed information and communications system in a micro-wave and millimeter wave band. Consequently, research into reducing energy loss in a power source/component used for a high power electronic device is being conducted.
A gallium nitride (GaN) based nitride semiconductor has been actively studied since the GaN based nitride semiconductor can easily be applied to a high frequency and high power electronic device as well as an optical device due to excellent properties such as a high energy gap, a high thermal and chemical stability, a high saturation velocity of about 3×107 cm/sec, and the like.
An electric device using the GaN based nitride semiconductor may have additional merits such as, a high breakdown electric field of about 3×106 V/cm, a maximized current density, a stable high-temperature operation, a high thermal conductivity, and the like. A heterostructure field effect transistor (HFET) using heterostructure semiconductor materials such as aluminum gallium nitride (AlGaN) and GaN may have a relatively high valence-band discontinuity at a heterojunction contact interface and thus, a high density of electrons may be induced and electron mobility may be enhanced, thereby enabling application in a high power device.
FIG. 1 illustrates a basic configuration of a conventional nitride-based HFET 10.
Referring to FIG. 1, the conventional nitride-based HFET 10 may include a low temperature buffer layer 12, a semi-insulating or high resistance GaN layer 13, and an AlGaN layer 15 each respectively formed in order on a sapphire substrate 11. A source electrode 16 and a drain electrode 18 may be formed at both ends of the AlGaN layer 15, and a gate electrode 17 may be formed between the source electrode 16 and the drain electrode 18.
The nitride-based HFET 10 may include a two-dimensional electron gas (2DEG) layer formed due to a heterostructure of the GaN layer 13 and the AlGaN layer 15 having different bandgaps. Here, a channel may be formed through the 2DEG layer in response to a signal inputted to the gate electrode 17, enabling a current to flow between the source electrode 16 and the drain electrode 18. The GaN layer 13 may be formed as a non-doped GaN layer having a relatively high resistance, to prevent a leakage current with respect to the sapphire substrate 11 and to isolate devices.